The present invention relates to peripherally flexible prop arches utilized in mining tracks, tunnels or the like.
Conventional peripherally flexible prop arches for a so called quandrant construction take up transverse forces resulted from bending loads which occur in the region of the connecting means of overlapping or superimposing gutter-profiled segments of the prop arch and produce against those forces or in connection with the flanges of only one gutter-shaped segment so called slide-in retarding forces of a required slide-in resistance.
In order to translate transverse and normal forces acting on the connecting means between the overlapping segments of the prop arch, which connection means is formed as a clamping device, the gutter-shaped segments have been made either cast formed, or the hook-like clamping device have been employed, which engaged with the flanges of the gutter-shaped segments. Both solutions, when utilized in practice, have the disadvantage that the segments of the prop arch in the region of the engagement with the clamping devices were supported not immediately against the rock structure and not between the rock structure surface and the support surface but the flanges of the clamping device were positioned between the flanges of the radially outwardly extended flanges of the segments of the arch and the rock structure. This led, during the insertion or sliding-in of the segments of the prop arch between the rock ceiling and the supporting floor, to a considerable and uncertain influence of the slide-in resistance which could result in a partial or total damage of the clamping device.
During the insertion of the peripherally flexible prop arch into a mining track with a strong pressure loading the arch is usually backfilled with a suitable construction material to improve supporting properties of the arch. To prevent an undesired rigidity of the prop arch it has been required to provide respective hollows in the backfilling material surrounding the arch, which has been labor-consuming and costly This auxiliary means, however has not totally eliminated the above noted disadvantages of conventional prop arches, in which the flanges of the gutter-shaped segments are engaged with the clamping devices so that these clamping devices remain hung on those flanges during the slide-in movement of the segments so that a further sliding-in movement becomes difficult or is blocked and in this case the peripheral flexibility of the prop arch is questioned.
One of flexible prop arches comprised of a plurality of gutter-shaped segments is disclosed in German patent publication No. K 11 585 5c, 9/10 published Dec. 17, 1953. The disadvantages of the known peripherally flexible arches are partially avoided in the above German publication in that the yokes of the clamping devices are engaged in the corresponding depressions of the flange end of the upper gutter-shaped segment in the region of the overlapping of the segments and the yokes do not overlay the flange ends directed toward the rock ceiling and thereby sliding of the arch along the rock is facilitated and it is ensured at the same time that the clamping devices during the insertion of the arch move together with the end of the inwardly positioned or upper gutter-shaped segment and specific auxiliary devices for this purpose are no longer necessary.
The basic shortcoming of the above described solution is that such a means is not secondary or additional when the yoke of the clamping device can be applied onto the overlapping ends of the segments because this yoke must slide on those ends to become engaged with the inwardly positioned or upper segment of the arch. Because of the necessity of such handling of the clamping device and because of the lowering of the rock, a significant relative displacement of the clamping device and the segments of the arch being clamped occurs, and the above discussed problem encountered in conventional arches remains generally unsolved, and such an arch has the disadvantage that the yoke of the clamping device, engaged with the flange of the inwardly positioned segment lies between the arch and the rock structure, and the slide-in ratio remains uncertain or uncontrollable because of an undesired increase of the given slide-in resistance.